November 29, 2010

Speed guns can help cops detect suicide bombers

Radar guns used by police to spot speeding motorists could help identify would-be suicide bomber in a crowd, say researchers. A radar gun fires microwave pulses at a car and measures the Doppler shift of the reflected signal to calculate its velocity. However, the strength and polarisation of the reflected signal – the radar cross section – can provide additional information about the size and shape of the reflecting object and the material it is made from. Researchers wondered whether the wiring in a suicide vest would alter the radar cross section of a bomber enough to allow a radar gun to pick him or her out in a crowd, reports New Scientist. To find out, William Fox of the Naval Postgraduate School in Monterey, California, and John Vesecky of the University of California, Santa Cruz, used software to simulate how radar signals at 1 gigahertz and 10 gigahertz would be reflected by the most common arrangements of looped wiring typically used by suicide bombers. They found that the clearest reflected signals were in the 10 gigahertz range. Together with colleague Kenneth Laws, they then fired low-power 10 gigahertz radar pulses at groups of volunteers, some wearing vests wired up like suicide vests. About 85% of the time, telltale factors in the polarisation of the reflected signals allowed them to correctly identify a “bomber” up to 10m away. The team now hopes that the US army will fund further development of the system, allowing them to boost the detection rate and include refinements to avoid false alarms being triggered by metal parts in underwired bras, jewellery and earphone leads. The researchers suggest military checkpoints would be major users of such a system – but it could also be installed alongside CCTV cameras in shopping malls, railway stations, airports and high streets.source:times of india